1. Field of the Invention
Foamed recyclables are molded, lightweight, two-polymer structured materials containing large amounts of industrial waste products. The physical properties of the cured products are excellent when compared to the properties of commercially available foams. The industrial waste products are fines, or must be converted to fines, prior to use in the foamed recyclable. The binder or glue that encapsulates each particle and forms the cellular walls of the foam is itself a unique, two-polymer thermoset that, when cured, allows maximum physical property attainment through polymer design.
Molded or processed foamed recyclables of the present invention are useful as, e.g., lightweight roofing materials (e.g., tiles or slates), decorative or architectural products, outdoor products, low cost insulation panels, fencing, lightweight, buoyant or corrosion-resistant marine products, etc.
2. Discussion of Related Art
Hybrid resins are known, and are described in Edwards, The Application Of Isophthalic Unsaturated Polyester Urethane Hybrids In Conventional Molding Techniques, 42nd Annual Conference Composites Institute, The Society Of The Plastics Industry, Inc., Feb. 2-6, (1987) (pp. 1-6, Session 8-C), U.S. Pat. No. 4,822,849, U.S. Pat. No. 4,892,919 and U.S. Pat. No. 5,086,084.
Interpenetrating polymer networks, or IPNs are also known. An IPN is a material which consists of a pair of networks, at least one of which has been synthesized and/or crosslinked in the presence of the other. An IPN can be described as an intimate mixture of two or more distinct crosslinked polymer networks that cannot be physically separated. Interpenetrating polymer networks can be classified into several categories. For example, when only one polymer is crosslinked and the other is linear, the product is called semi-IPN. U.S. Pat. No. 4,302,553 discloses two structurally different crosslinked polymers, which when combined, form an IPN structure. The IPN structure is comprised of the two different crosslinking polymers which are permanently entangled with one another and characterized in that no chemical interaction had occurred between the individual networks. Interpenetrating polymer networks are also described in U.S. Pat. No. 4,923,934 and U.S. Pat. No. 5,096,640.
Foamed and/or cured foams of polymer resins, which may contain inorganic fillers, are described in U.S. Pat. No. 2,642,403, U.S. Pat. No. 3,697,456, U.S. Pat. No. 4,331,726, U.S. Pat. No. 4,725,632, U.S. Pat. No. 4,777,208, U.S. Pat. No. 4,816,503, U.S. Pat. No. 4,216,294, U.S. Pat. No. 4,260,538, U.S. Pat. No. 4,694,051, and U.S. Pat. No. 4,946,876.
Despite this activity, the products produced by the prior art, especially products of lightweight construction materials, do not have sufficiently well-balanced properties with regard to structural strength, as well as with regard to corrosion and thermal resistance, and processing.
Preparation of foams of unsaturated polyesters useful in the manufacture of lightweight building materials has been attempted using a number of different techniques. However, a difficulty encountered in attempts to produce unsaturated polyester foams is the generation of gases so as to cause a uniform expansion of the resin at ambient temperatures before any appreciable crosslinking occurs. The present inventor has discovered that with a two polymer system, a significant portion of the crosslinking and curing does not have to occur immediately after the maximum amount of gases has been released. Indeed, upon completion of the first polymer reaction, the crosslinking reaction can be delayed for hours. However, should appreciable crosslinking occur before maximum gas release, the accompanying exothermic reaction will cause cracking as the previously unreleased gases are generated thereby causing stresses against a very rigid crosslinked structure which is unable to further expand. Moreover, should the polyurethane reaction have not occurred to a point sufficient to maintain the cell structures, the gases will gradually escape, and the expanded resin will drop back to its original state. The cured polymer will form much like a standard resin casting, with little or no expansion.
Lightweight cementitious compositions are known in which the desired weight reduction over concrete is achieved by the use of lightweight aggregate. However, articles made from such materials are brittle and possess tensile strengths which are low and limit many practical applications. Also, the density range of lightweight concretes is three times higher than the foam of the present invention.
Low density rigid polyurethane modified-polyisocyanurate foams have been widely used as insulative structural members. As with other polymeric materials, it is often desirable to reduce the polymer content and improve the properties of these members by the addition of inorganic fillers. Unfortunately, it has proven difficult to provide a rigid polyurethane or polyisocyanurate foam containing more than about 10% by weight of such fillers. These fillers tend to rupture the cells of the foam, which in turn dramatically reduces its insulative capacity. Another undesirable effect of high levels of fillers is that the foam becomes very friable. Since higher filler levels are desired, because they provide a less expensive material and certain physical property improvements, it would be highly desirable to provide a highly filled, rigid polyurethane-modified polyisocyanurate foam which has good insulative properties and low friability.
U.S. Pat. No. 4,661,533 relates to using a particular inorganic filler, namely fly ash, as the inorganic filler for filling rigid polyurethane modified-polyisocyanurate foams. High percentage additions of fly ash to very light weight (2 pounds per cubic foot (pcf)) insulating foam are described. The use of the fly ash inorganic filler enables the foam to be filled to a theoretical level of about 80% of the foam's total weight without deterioration of the insulative properties, friability and compressive strength. The foam is useful as board insulation, sheathing insulation, pipe insulation and the like. However, even though the foam of the above patent is highly filled with fly ash, the problems associated with the formation of two distinct polymers and hybrid resin technology where a very high percentage of the end product is crosslinkable as a cured polyester (up to 90%) did not have to be addressed. Additionally, the superior processing advantages inherent in the polyester/polyurethane chemistry are not possible with the prior art product. The potential physical properties obtainable from the filled foam of the present invention, having two distinct polymer systems, are much higher, and the ability to control individual reactions in the polyester/polyurethane system used in the present invention is considerably better than that possible with the single shot polyurethane/polyisocyanurate chemistry of the prior art.